Open AccessCalcium‐dependent binding of basement membrane protein BM‐40 (osteonectin, SPARC) to basement membrane collagen type IV
Author(s) -
MAYER Ulrike,
AUMAILLEY Monique,
MANN Karlheinz,
TIMPL Rupert,
ENGEL Jürgen
Publication year - 1991
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1991.tb15996.x
Subject(s) - osteonectin , basement membrane , chemistry , binding site , biophysics , extracellular matrix , triple helix , calcium , biochemistry , circular dichroism , stereochemistry , biology , microbiology and biotechnology , enzyme , alkaline phosphatase , organic chemistry , osteocalcin
Basement membrane protein BM‐40, prepared from the mouse Engelbreth‐Holm‐Swarm tumor, was used in native, denatured and proteolytically processed form for binding to various extracellular matrix proteins. BM‐40 and its derivatives were also characterized by CD spectroscopy, calcium binding and epitope analysis. Of several basement membrane proteins tested only collagen IV showed a distinct and calcium‐dependent binding of BM‐40 in an immobilized ligand assay. This interaction was specific as shown by a low activity of other collagen types (I, III, V, VI) in direct binding and competition assays. The binding was reduced or abolished by metal‐ionchelating or chaotropic agents, high salt and reduction of disulfide bonds in BM‐40. Fragment studies indicated that domains III (α‐helix) and/or IV (EF hand) of BM‐40 possess the binding site(s) for collagen IV, while the N‐terminal domains I and II provide the major antigenic determinants. A major BM‐40‐binding site on collagen IV was dependent on a triple‐helical conformation and could be localized to a pepsin fragment from the central portion of the triple‐helical domain, in agreement with electron microscopic visualization of BM‐40 – collagen‐IV complexes.